There are many different situations in which safety concerns require that mechanisms must be provided for quickly shutting off a valve or the like in potentially dangerous circumstances. For instance, in relation to fuel tankers (including both road and rail tankers) it has long been a requirement to provide a mechanism for shutting off the valve from a remote position in the event of a leakage or similar accident. Conventionally this is done by fitting a boden cable to the operating lever of the valve, the cable extending around the periphery of the tanker so that the valve can be closed simply by pulling on the cable from any position around the tanker.
More recent safety regulations specify not only that it must be possible to manually close a fluid discharge valve from a remote position, but also that the valve must close automatically in the event of a fire. Clearly re-designing and replacing all existing discharge valves with valves designed to close in the event of a fire would be a massive and expensive operation. It is therefore an object of the present invention to obviate the need to re-design or replace conventional discharge valves.
According to a first aspect of the present invention there is provided a temperature dependent actuating device for a valve having a closure member which must be moved from a first to a second position to close the valve, the actuating device comprising a body, an actuating member supported by the body and moveable relative to the body from a first non-actuating position to a second actuating position, biasing means which urges the actuating member towards the second position, and temperature dependent means for releasably retaining the actuating member in said first position against the biasing action of the biasing means provided the temperature is below a predetermined level, wherein said body is adapted to be mounted adjacent the valve with said actuating member positioned to engage the valve closure member, such that if the temperature in the immediate vicinity of the valve rises above said predetermined temperature said actuating member is released from said first position and is biased to its second position thereby moving the valve closure member from its first to its second position and closing the valve.
The present invention thus provides an actuating device which may be retro-fitted to existing valve assemblies and which responds to temperatures in the immediate vicinity of the valve assembly to shut the valve in the event of the temperature rising to a dangerous level. The xe2x80x9cpredetermined temperaturexe2x80x9d may not be determined precisely, what is important is that the actuating member will be activated in the event of a dangerous situation such as a fire.
The body of the actuating device may have fixing means, such as flanges etc, designed to mate with flanges or the like of conventional valve assemblies. Alternatively, a separate bracket or clamp arrangement may be provided to mount the actuating device to the valve assembly.
Movement of the actuating member may either push or pull the operating mechanism into the closed position.
Suitably, when in said first position the actuating member is clear of the closure member but strikes the closure member when released into its second position thereby pushing the closure member into the closed position.
Alternatively, the actuating member is connected to the closure member via a linkage, the linkage being arranged to translate movement of the actuating member to movement of the valve closure member from its first position to its second position, thereby closing the valve.
Preferably, said biasing means comprises a coil spring which is under compression when said actuating member is held in said first position.
Suitably, the first position of the actuating member is a retracted position (relative to the body) and the second position is an extended position (relative to the body) and
The temperature dependent release means preferably comprises a fusible material, such as a relatively low melting point metal or metal alloy (e.g. a solder). In preferred embodiments the fusible material is used to weld the actuating member in said first position relative to the body so that when the temperature rises above the predetermined temperature the weld melts and the actuating member is released.
According to a second aspect of the present invention there is provided a temperature dependent actuating device comprising a body, an actuating member supported by the body and moveable relative to the body from a first retracted position to a second actuating position in which it extends from the body, biasing means which urges the actuating member towards the second position, and means comprising a body of fusible material for releasably retaining the actuating member in said first position against the action of the biasing member, wherein said body of fusible material is selected to melt at a temperature above a predetermined temperature thereby releasing said actuating member.
Preferably when in said retracted position the actuating member is received entirely within the body. This need not necessarily be the case and a portion (or even all) of the actuating member may extend from the body when in said first position in which case the actuating member will extend further from said body when in said second position.
According to a third aspect of the present invention there is provided a valve assembly comprising a closure member which must be moved from a first to a second position to close a valve, and a actuating member positioned to engage the valve closure member, the actuating member being supported by a body and being moveable relative to the body from a first non-actuating position to a second actuating position, temperature dependent means being provided for releasably retaining the actuating member in said first position against the biasing action of a biasing means which urges the actuating member towards the second position, the arrangement being such that a rise in temperature in the immediate vicinity of the valve assembly above a predetermined temperature causes said retaining means to release the actuating member so that the actuating member is biased to its second position thereby moving the valve closure member from its first to its second position and closing said valve.